RU2569174C1 - Ceramic waveguide microwave filter - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: disclosed is a ceramic microwave filter consisting of a metal-coated ceramic unit in the form of a rectangular parallelepiped, in which a line of directly coupled cavity resonators is formed, and input and output communication elements situated on the end faces with an adapter on the lower face of the unit are in the form of a series connection of an inductive slit and a section of a coplanar line.

EFFECT: broader capabilities of filter adjustment, which enable to match the filter with input and output lines for a wider range of filter parameter values based on a basic ceramic unit.

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Description

The invention relates to microwave electronics and is intended for use in frequency selection devices, mainly in the centimeter and millimeter wavelength ranges.

Known waveguide ceramic microwave filter, consisting of a metallized ceramic block in the form of a rectangular parallelepiped, in which a chain of volume resonators is formed, with communication elements in the form of capacitive pads on the lower edge of the block [US 2009/0231064 A1, Sep. 17, 2009]. One of the disadvantages of this filter is the inconvenience of setting up communication elements located on the lower edge of the block.

The closest in technical solution is the waveguide ceramic microwave filter adopted for the prototype, consisting of a metallized ceramic block in the form of a rectangular parallelepiped, in which a chain of volume resonators with direct coupling is formed, and the input and output coupling elements are made in the form of short-circuited segments of coplanar lines on the end faces ceramic block and open at the ends of the segments of coplanar lines on the lower edge of the ceramic block. The ability to change the length of short-circuited segments of coplanar lines on the end faces of the ceramic block allows you to fine-tune the matching of the filter with the input and output transmission lines after installing the filter on the board [RU 2462799].

The main disadvantage of this filter is that the communication elements in the form of segments of coplanar transmission lines have limitations on the coupling coefficient with the input and output resonators, due to structural restrictions on the length of these lines, which, in turn, leads to a limitation of the range realized using such communication elements filter options.

The technical result of the invention is the expansion of filter tuning capabilities, allowing filter matching with input and output lines for a wider range of filter parameters (bandwidth, etc.) based on a basic ceramic block.

To achieve the above technical result, a ceramic microwave filter is proposed, consisting of a metallized ceramic block in the form of a rectangular parallelepiped, in which a chain of volume resonators with direct coupling is formed, and the input and output communication elements located on the end faces with the transition to the lower face of the block are made in the form serial connection of the inductive gap and the segment of the coplanar line.

The matching of the filter with the input and output transmission lines is achieved by choosing the optimal values of the inductances of the communication elements L _p0 , L _{pn + 1} and the mutual induction coefficients M _0,1 , M _{n, n + 1.}

The specified filter characteristics determine the required coupling coefficient between the input resonator and the input line [1].

where w is the relative bandwidth of the filter;

q ₀ , q ₁ - elements of the low-pass filter prototype.

On the other hand, for a chain of resonators with inductive coupling

where M _0,1 , L _r0 , L _{r1 are} determined by the geometry of the input resonator and the coupling element.

The expansion of the filter settings can be obtained by increasing the range of realizable values of inductances and coefficients of mutual induction of communication elements when connecting the inductive gap and the segment of the coplanar line.

The invention is illustrated by drawings.

In FIG. 1 shows a coupling element of a ceramic waveguide filter made on the end faces of a block in the form of a series connection of an inductive gap and a segment of a coplanar line.

In FIG. 2 presents an equivalent circuit of a chain of volume resonators with direct inductive coupling, with input and output inductive coupling elements [1].

In FIG. 3 shows a resonator model associated with a transmission line, implemented in a three-dimensional electromagnetic simulation program.

In FIG. 4 and FIG. 5 shows the results of modeling communication elements (Fig. 4 is an analog communication element), (Fig. 5 is a proposed communication element).

The relationship between the filter parameters and the geometry of the communication element can be established using the technique of tuning the input and output resonators of the filter [2] and three-dimensional electromagnetic resonator simulation programs associated with the transmission line.

The frequency response of a single input resonator is analyzed, which is connected through the studied communication element to the input transmission line and using a probe with weak coupling to the output transmission line. The resonator resonance curve width is measured at a level of 3 dB (Δf), which is related to the filter bandwidth (Δf _n ):

where q ₁ is the value of the first element of the prototype filter, determined by the filter parameters (type of characteristic, non-uniformity of the characteristic, coefficient of squareness, number of links).

The realized filter band is q ₁ times larger than the width of the resonance curve of the resonator. Depending on the filter parameters, q ₁ for a filter with a Chebyshev characteristic most often ranges from 0.7 to 2.13.

We analyzed the input resonator with dimensions of 3.7 × 3.7 × 2.2 mm, with a dielectric constant of the material ε = 10, with an analog coupling element in the form of a segment of a coplanar line shorted at the end, and with the claimed coupling element (slot width of the coupling element bz = 0.3 mm).

The simulation results show that the proposed element allows to increase the implemented range of the filter bandwidth by more than 2 times.

The element of communication of the ceramic waveguide filter with transmission lines works as follows:

After the microwave signal arrives at the input line in the segment of the coplanar line and the slit, an electromagnetic field is excited in which the magnetic field lines in the direction coincide with the magnetic field lines of the input filter resonator operating on the H ₁₀₁ oscillations of a rectangular resonator. The flux linkage of the magnetic fields of the coupling element and the input resonator provides an efficient input of energy from the input line to the filter, which is a chain of resonators with direct coupling. The energy output is carried out in the reverse order by the output coupling element.

The communication elements are tuned for optimal matching of the filter with the input and output communication lines by selecting the length of the communication gap.

Literature

[1] Microwave filters, matching circuits and communication circuits, G.L. Matthew, L. Young, E.M.T. Jones, vol. 2, 1988, 495 pp.

[2] Reference on elements of strip technology / Mazepova OI, Meshchanov VP, Prokhorova NI, Feldstein A.L. / ed. A.L. Feldstein. - M.: Communication, 1979.

Claims (1)

A waveguide ceramic microwave filter in the form of a rectangular parallelepiped made of thermostable ceramic material, on all faces of which a metallization is deposited, in which a chain of volume resonators is formed, input and output communication elements, characterized in that the input and output communication elements on the end faces of the block are made in the form of a sequential connection of the inductive gap and the segment of the coplanar line.

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